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1、附錄三附錄三外文文獻(xiàn)原文及譯文外文文獻(xiàn)原文及譯文原文:AnevaluationofNDTmethodsfthelocationsizingoffgingdiscontinuitiesIninganNDTmethodfflawdetectioninfgingsanumberofvariablesmustbeconsidered:a)thetypeofdiscontinuitytobeassessedb)themethodtobeusedf
2、detectionevaluationc)thevariablesassociatedwiththefgingitselfThevariablesinitema)willgovernthelocationwithinthefgingitsientationwithrespecttoaparticularsurfaceItemb)couldincludeaconsiderablearrayofNDTmethodsbutfthepurpos
3、eofthispaperonlythesixmostwidelyusedareconsidered一visualtesting(VT)perantinspection(PI)magicparticleinspection(MI)eddycurrenttesting(ET)radiographicinspection(RT)ultrasonicinspection(UI).Inthelastitemc)thecomponentracein
4、cludesuchthingsasconditiongeometryaccessfinspection.a)FgingdiscontinuitiesThelocationofthediscontinuitywillhaveasignificantinfluenceontheionoftheNDTmethodtobeusedtheyaretherefegroupedintothreecategiestoaidthision:1.opent
5、othesurface:lapsseamburstslugscracksinclusions2.slightlysubsurface:seamstringersinclusionsgrainstructurevariations3.internal:stringersburstlaminationgrainstructureinclusionspipingAbriefreviewofthesetermsmaybehelpful:Lap:
6、foldedmetalflattenedintothesurfacebutnotfusingwithitSeam:linearflawsduetooxidizedblowholesingotsplasheswhichareelongatedbyhotwkingBurst:rupturescausedbyfailureofplasticdefmationbyprocessingattoolowatemperatureexcessivewk
7、ingofmetalStringers:abarstockdefectduetononmetallicinclusionsbeingsqueezedoutintolongthinstringsLamination:planardefectalignedparalleltosurfaceiginatingintheiginalingotfromrolledoutpipingCracks:transgranularfailureduetol
8、ocalizedstressesresultingfromnonunifmheatingcoolingnonplasticdefmationInclusions:impuritiessuchasslagoxidesulphidesoftenfromtheiginalmoltenstageinfmingthebilletusedffgingtotalbeingimpedance.Thisimpedancealsocausesalagbet
9、weenthecurrentthevoltagecalledaphaseshift.Thisshiftimpedanceareacteristicsofthecoil.Ifthecoilisnowplacedclosetoaconductingsurfacethereversingmagicfieldinducesareversingcurrentintheconducting(eddycurrent)whichopposesthein
10、ducingfield.Thisoppositionalterstheimpedanceofthecoilasuitableinstrumentcandetectthesechanges(bothphaseangleimpedance).Fagivendiscontinuityfreesurfaceaspecificalterationwillbepresentwhichcanbezeroed.Ifthecoilnowpassesove
11、radiscontinuityachangeininductionwilloccurwhichwillberegisteredbytheinstrument.Howeverachangeintheconductivityofthematerialwillalsoeffecttheinductionaswillchangesinpermeability.Thusnonunifmheattreatmentsegregationinhomog
12、eneitiesinmaterialcompositionstructurewillalsoeffecttheinductioncreatean‘indication’.Anothercriticalfactisthedistancebetweenthecoilthetestsurface.This‘liftoff’canbeusedinapositivewaytodeterminecoatingpaintthickness’oncon
13、ductingmaterials.Butequallydifferencesinthecoilspecimengapcanresultinnonrelevantsignals.Thesystemcantherefedetectsurfaceslightsubsurfacediscontinuities.Howeverthisisonlypossibleinconductingmaterialstheproximityofthetestc
14、oiltothetestsurfaceiscritical.Thismeansthatfanycomponent(otherthanflatplate)specialprobesareusuallydesignedtofollowspecificcomponentcontours.Asmalleddycurrentmachinecancostaslittleas$2000butalargeautomatedmachinecancostu
15、pto$20000RT一Shtwavelengthelectromagicradiationwillpassthroughmanymaterialsdependingupondensitythicknessthencreatearangeofexposuresoneitherfilmafluoscopicscreentopresentavisualimageoftheinternalcompositionoftheitem.Differ
16、encesinabsptionwithinthematerialduetosuchthingsasgasholescracksburstswillcreatephotographicdensitydifferencesonthefilmdetectwhichcanbeinterpretedbytrainedpersonnel.ThesourceofradiationcanbeanXraytubeagammasource(suchasIr
17、idiumCobalt)theimagescanbegeneratedoneitherfilmasrealtimeimagesonfluoscopicscreens.Defectientationisavitalfactinradiographysinceitisthicknessdifferenceswhichtheprocessdetects.Hencealaminationtypedefectparalleltothefilmwo
18、uldbealmostimpossibletodetect.Ontheotherhacrackperpendiculartothefilmwouldalmostcertainlybedetected.Itistherefeoftenthecasethatasinglecomponentwouldhavetoberadiographedfrommethanonedirectionindertodetectmostdefects.Final
19、lytheradiationusedishighlyhazardoustherefeanyenvironmentinwhichitisusedmustsuitablyshieldedtopreventexposureoftheoperat.AswellasshieldingtheuseofXgammarayswillalsorequiremonitsalarmsinterlockspersonaldosimetrysystemswhic
20、halongwiththefilmitselfaddstothecost.AbasicXraysetupwouldcostaround$10000withancillaryequipmentfilmcouldcost$3000peryeartorun.UT—Ataninterfacebetweenmaterialsofdifferingacousticimpedanceasoundwavewillhaveaproptionreflect
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